Semiconducting materials based on naphthalenediimide-vinylene-oligothiophene-vinylene polymers

ABSTRACT

The present invention provides a polymer comprising a unit of formula, 
                         
wherein
     R 1  and R 2  are independently from each other C 1-30 -alkyl, C 2-30 -alkenyl, C 2-30 -alkynyl, phenyl or a 5 to 8 membered heterocyclic ring system, wherein
       each of the C 1-30 -alkyl, C 2-30 -alkenyl or C 2-30 -alkynyl group may be substituted with 1 to 10 substituents independently selected from the group consisting of halogen, —CN, —NO 2 , —OH, —NH 2 , —NH(C 1-20 -alkyl), —N(C 1-20 -alkyl) 2 , —NH—C(O)—(C 1-20 -alkyl), —S(O) 2 OH, —CHO, —C(O)—C 1-20 -alkyl, —C(O)OH, —C(O)—OC 1-20 -alkyl, —C(O)NH 2 , —CO(O)NH—C 1-20 -alkyl, —C(O)N(C 1-20 -alkyl) 2 , —O—C 1-20 -alkyl, —O—C(O)—C 1-20 -alkyl, —SiH 3 , SiH 2 (C 1-20 -alkyl), SiH(C 1-20 -alkyl) 2 , Si(C 1-20 -alkyl) 3 , C 4-8 -cycloalkyl, phenyl and a 5 to 8 membered heterocyclic ring system, and phenyl and the 5 to 8 membered heterocyclic ring system may be substituted with 1 to 5 C 1-16 -alkyl groups,   
       is 1, 2 or 3   and   n is an integer from 2 to 10&#39;000,   a process for the preparation of the polymer and an electronic device comprising the polymer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application (under 35 U.S.C. §371) of PCT/IB2013/060880, filed Dec. 12, 2013, which claims benefit of European Application No. 12197747.4, filed Dec. 18, 2012, both of which are incorporated herein by reference in their entirety.

Organic semiconducting materials can be used in electronic devices such as organic photovoltaic devices (OPVs), organic field-effect transistors (OFETs), organic light emitting diodes (OLEDs), and organic electrochromic devices (ECDs).

For efficient and long lasting performance, it is desirable that the organic semiconducting material-based devices show high charge carrier mobility as well as high stability, in particular towards oxidation by air.

Furthermore, it is desirable that the organic semiconducting materials are compatible with liquid processing techniques such as spin coating, inkjet printing and gravure printing. These liquid processing techniques are convenient from the point of processability, and thus allow the production of low cost organic semiconducting material-based electronic devices. In addition, liquid processing techniques are also compatible with plastic substrates, and thus allow the production of light weight and mechanically flexible organic semiconducting material-based electronic devices.

The organic semiconducting materials can be either p-type or n-type organic semiconducting materials. It is desirable that both types of organic semiconducting materials are available for the production of electronic devices.

The use of naphthalene diimide (NDI) based polymers as semiconducting materials in electronic devices is known in the art.

Durban, M. M.; Kazarinoff, P. D.; Segawa, Y.; Luscombe. C. K. Macromolecules 2011, 44, 4721 to 4727 describe highly soluble naphthalenediimide (NDI) polymers. Average electron mobilities as high as 0.0026 cm² V⁻¹ s⁻¹ are reported for the naphthalene diimide (NDI) polymer PNDI-2BocL having the following structure:

Sajoto, T.; Tiwari, S. P.; Li, H.; Risko, C.; Barlowa, S.; Zhang, Q.; Cho, J.-Y.; Brédas, J.-L.; Kippelen, B.; Marder, S. R. Polymer, 2012, 53, 5, 1072 to 1078 describe copolymers having the following structure:

These copolymers show average electron mobility values ranging from 1.4×10⁻⁴ to 3.7×10⁻³ cm² V⁻¹ s⁻¹.

Zhou, W.; Wen, Y.; Ma, L.; Liu, Y.; Zhan, X. Macromolecules 2012, 45, 4115 to 4121 describe naphthalene diimide (NDI) and phenothiazine (PTZ) based copolymers having the following structure:

These copolymers exhibit electron mobilities as high as 0.05 cm² V⁻¹ s⁻¹ and on/off ratios as high as 10⁵ under nitrogen atmosphere.

Yan, H.; Chen, Z.; Zheng, Y., Newman, C.; Quinn, J. R.; Dötz, F. Kastler, M.; Facchetti, A. Nature, 2009, 457, 679 to 687 and Chen, Z.; Zheng, Y.; Yan, H.; Facchetti, A. J. Am. Chem. Soc. 2009, 131, 8 to 9 describe naphthalene diimide (NDI) and bithiophene based copolymer having the following structure:

These copolymers show excellent mobility values of up to 0.45 to 0.85 cm² V⁻¹ s⁻¹.

WO 2009/098253 describes polymers of general formula -(-M₁-M₂)_(n)-, wherein M₁ is an optionally substituted naphthalene imide selected from

and M₂ is selected from a list of residues including Z—(—Ar—)_(m″)—Z—.

Guo, X.; Kim, F. S.; Seger, M. J.; Jenekhe, S. A.; Watson, M. D. Chem. Mater. 2012, 24, 1434 to 1442 describe a series of alternating donor-acceptor copolymer semiconductors based on naphthalene diimide (NDI) acceptor and seven different thiophene moieties having the following structures:

R=2-decyltetradecyl, 2-ethylhexyl, n-dodecyl, n-octyl.

These copolymers display n-channel or ambipolar mobility as high as 0.07 cm²V⁻¹s⁻¹.

It was the object of the present invention to provide improved new organic polymeric semiconducting materials.

The object is solved by the polymers, processes and devices described herein.

The organic polymeric semiconducting material of the present invention is a polymer comprising a unit of formula,

wherein R¹ and R² are independently from each other C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl, C₂₋₃₀-alkynyl, phenyl or a 5 to 8 membered heterocyclic ring system, wherein

-   -   each of the C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl or C₂₋₃₀-alkynyl group         may be substituted with 1 to 10 substituents independently         selected from the group consisting of halogen, —CN, —NO₂, —OH,         —NH₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂,         —NH—C(O)—(C₁₋₂₀-alkyl), —S(O)₂OH, —CHO, —C(O)—C₁₋₂₀-alkyl,         —C(O)OH, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl,         —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, —O—C(O)—C₁₋₂₀-alkyl,         —SiH₃, SiH₂(C₁₋₂₀-alkyl), SiH(C₁₋₂₀-alkyl)₂, Si(C₁₋₂₀-alkyl)₃,         C₄₋₈-cycloalkyl, phenyl and a 5 to 8 membered heterocyclic ring         system, and phenyl and the 5 to 8 membered heterocyclic ring         system may be substituted with 1 to 5 C₁₋₁₆-alkyl groups,         o is 1, 2 or 3         and         n is an integer from 2 to 10'000.

Examples of halogen are —F, —Cl, —Br and —I.

C₁₋₆-alkyl, C₁₋₁₀-alkyl, C₁₋₁₆-alkyl, C₁₋₃₀-alkyl, C₆₋₃₀-alkyl and C₁₀₋₃₀-alkyl can be branched or unbranched. Examples of C₁₋₆-alkyl are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, isopentyl, n-(1-ethyl)propyl and n-hexyl. Examples of C₁₋₁₀-alkyl are C₁₋₆-alkyl, n-heptyl, n-octyl, n-(2-ethyl)hexyl, n-nonyl and n-decyl. Examples of C₁₋₁₆-alkyl are C₁₋₁₀-alkyl, n-undecyl, n-dodecyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl and n-hexadecyl. Examples of C₁₋₂₀-alkyl are C₁₋₁₀-alkyl, n-undecyl, n-dodecyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-icosyl (C₂₀) and n-(2-octyl)dodecyl. Examples of C₁₋₃₀-alkyl are C₁₋₂₀-alkyl, and n-docosyl (C₂₂), n-tetracosyl (C₂₄), n-(2-decyl)tetradecyl, n-hexacosyl (C₂₆), n-octacosyl (C₂₈) and n-triacontyl (C₃₀). Examples of C₆₋₃₀-alkyl are n-hexyl, n-heptyl, n-octyl, n-(2-ethyl)hexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl and n-icosyl (C₂₀), n-(2-octyl)dodecyl, n-docosyl (C₂₂), n-tetracosyl (C₂₄), n-(2-decyl)tetradecyl, n-hexacosyl (C₂₆), n-octacosyl (C₂₈) and n-triacontyl (C₃₀). Examples of C₁₀₋₃₀-alkyl are n-decyl, n-undecyl, n-dodecyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl and n-icosyl (C₂₀), n-(2-octyl)dodecyl, n-docosyl (C₂₂), n-tetracosyl (C₂₄), n-(2-decyl)tetradecyl, n-hexacosyl (C₂₆), n-octacosyl (C₂₈) and n-triacontyl (C₃₀).

C₂₋₃₀-alkenyl and C₆₋₃₀-alkenyl can be branched or unbranched. Examples of C₂₋₃₀-alkenyl are vinyl, propenyl, cis-2-butenyl, trans-2-butenyl, 3-butenyl, cis-2-pentenyl, trans-2-pentenyl, cis-3-pentenyl, trans-3-pentenyl, 4-pentenyl, 2-methyl-3-butenyl, hexenyl, heptenyl, octenyl, nonenyl and docenyl, linoleyl (C₁₈), linolenyl (C₁₈), oleyl (C₁₈), arachidonyl (C₂₀), and erucyl (C₂₂). Examples of C₆₋₃₀-alkenyl are hexenyl, heptenyl, octenyl, nonenyl and docenyl, linoleyl (C₁₈), linolenyl (C₁₈), oleyl (C₁₈), arachidonyl (C₂₀), and erucyl (C₂₂).

C₂₋₃₀-alkynyl and C₆₋₃₀-alkynyl can be branched or unbranched. Examples of C₂₋₃₀-alkynyl are ethynyl, 2-propynyl, 2-butynyl, 3-butynyl, pentynyl, hexynyl, heptynyl, octynyl, nonynyl, decynyl, undecynyl, dodecynyl, undecynyl, dodecynyl, tridecynyl, tetradecynyl, pentadecynyl, hexadecynyl, heptadecynyl, octadecynyl, nonadecynyl and icosynyl (C₂₀). Examples of C₆₋₃₀-alkynyl are hexynyl, heptynyl, octynyl, nonynyl, decynyl, undecynyl, dodecynyl, undecynyl, dodecynyl, tridecynyl, tetradecynyl, pentadecynyl, hexadecynyl, heptadecynyl, octadecynyl, nonadecynyl and icosynyl (C₂₀).

Examples of C₄₋₈-cycloalkyl are cyclobutyl, cyclopentyl, cycloexyl, cycloheptyl and cyclooctyl.

Examples of 5 to 8 membered heterocyclic systems are pyrrolidinyl, 1-pyrrolinyl, 2-pyrrolinyl, 3-pyrrolinyl, tetrahydrofuryl, 2,3-dihydrofuryl, tetrahydrothiophenyl, 2,3-dihydrothiophenyl, imidazolidinyl, imidazolinyl, pyrazolidinyl, pyrazolinyl, oxazolidinyl, oxazolinyl, isoxazolidinyl, isoxazolinyl, thiazolidinyl, thiazolinyl, isothiazolidinyl and isothiazolinyl, 1,2,3-triazolyl, 1,2,4-triazolyl, 1,4,2-dithiazolyl, piperidyl, piperidino, tetrahydropyranyl, pyranyl, thianyl, thiopyranyl, piperazinyl, morpholinyl, morpholino, thiazinyl, azepanyl, azepinyl, oxepanyl, thiepanyl, thiapanyl, thiepinyl, 1,2-diazepinyl, 1,3-thiazepinyl, pyrrolyl, furyl, thiophenyl, imidazolyl, pyrazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, oxadiazolyl, tetrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, 1,2,3-triazinyl, 1,2,4-triazinyl, 1,3,5-triazinyl, azepinyl and 1,2-diazepinyl.

Examples of alkali metals are sodium, potassium and lithium.

Examples of alkaline earth metals are calcium and magnesium.

Preferably, the organic polymeric semiconducting material of the present invention is a polymer comprising preferably at least 80% by weight, more preferably at least 90% by weight, of a unit of formula (1), based on the weight of the polymer.

More preferably, the organic polymeric semiconducting material of the present invention is a polymer consisting essentially of a unit of formula (1).

Preferably, R¹ and R² are independently from each other C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl, C₆₋₃₀-alkynyl, or phenyl,

-   -   wherein each of the C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl         group may be substituted with 1 to 10 substituents independently         selected from the group consisting of halogen, —CN, —NO₂, —OH,         —NH₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂,         —NH—C(O)—(C₁₋₂₀-alkyl), —S(O)₂OH, —CHO, —C(O)—C₁₋₂₀-alkyl,         —C(O)OH, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl,         —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, and N—O—C(O)—C₁₋₂₀-alkyl,         and phenyl may be substituted with 1 or 2 C₁₋₁₆-alkyl groups.

More preferably, R¹ and R² are independently from each other C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl,

-   -   wherein each of the C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl         group may be substituted with 1 to 10 substituents independently         selected from the group consisting of halogen, —CN, —NO₂,         —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂, —NH—C(O)—(C₁₋₂₀-alkyl),         —C(O)—C₁₋₂₀-alkyl, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂,         —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, and         N—O—C(O)—C₁₋₂₀-alkyl.

Even more preferably, R¹ and R² are independently from each other C₆₋₃₀-alkyl,

-   -   wherein each of the C₆₋₃₀-alkyl may be substituted with 1 to 10         substituents independently selected from the group consisting of         halogen, —CN, —NO₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂,         —NH—C(O)—(C₁₋₂₀-alkyl), —C(O)—C₁₋₂₀-alkyl, —C(O)—OC₁₋₂₀-alkyl,         —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂,         —O—C₁₋₂₀-alkyl, and N—O—C(O)—C₁₋₂₀-alkyl.

Most preferably, R¹ and R² are independently from each other C₁₀₋₃₀-alkyl, in particular 2-octyldodecyl.

Preferably, o is 1 or 2.

n is preferably an integer from 5 to 1'000, more preferably an integer from 5 to 500, most preferably an integer from 10 to 100.

Preferred polymers comprising a unit of formula (1) are polymers,

wherein

R¹ and R² are independently from each other C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl, C₆₋₃₀-alkynyl, or phenyl, wherein each of the C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl group may be substituted with 1 to 10 substituents independently selected from the group consisting of halogen, —CN, —NO₂, —OH, —NH₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂, —NH—C(O)—(C₁₋₂₀-alkyl), —S(O)₂OH, —CHO, —C(O)—C₁₋₂₀-alkyl, —C(O)OH, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, and N—O—C(O)—C₁₋₂₀-alkyl, and phenyl may be substituted with 1 or 2 C₁₋₁₆-alkyl groups. o is 1, 2 or 3 and n is an integer from 5 to 1'000.

More preferred polymers comprising a unit of formula (1) are polymers,

wherein

R¹ and R² are independently from each other C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl,

-   -   wherein each of the C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl         group may be substituted with 1 to 10 substituents independently         selected from the group consisting of halogen, —CN, —NO₂,         —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂, —NH—C(O)—(C₁₋₂₀-alkyl),         —C(O)—C₁₋₂₀-alkyl, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂,         —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, and         N—O—C(O)—C₁₋₂₀-alkyl,         o is 1, 2 or 3         and         n is an integer from 5 to 500.

Most preferred polymers comprising a unit of formula (1) are polymers,

wherein

R¹ and R² are independently from each other C₆₋₃₀-alkyl,

-   -   wherein each of the C₆₋₃₀-alkyl may be substituted with 1 to 10         substituents independently selected from the group consisting of         halogen, —CN, —NO₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂,         —NH—C(O)—(C₁₋₂₀-alkyl), —C(O)—C₁₋₂₀-alkyl, —C(O)—OC₁₋₂₀-alkyl,         —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂,         —O—C₁₋₂₀-alkyl, and N—O—C(O)—C₁₋₂₀-alkyl,         o is 1 or 2         and         n is an integer from 10 to 100.

Particular preferred polymers comprising a unit of formula (1) are polymers comprising a unit of

wherein n is an integer from 20 to 100, preferably around 60.

Also part of the invention is a process for the preparation of the polymers comprising a unit of formula

wherein R¹ and R² are independently from each other C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl or C₂₋₃₀-alkynyl, phenyl or a 5 to 8 membered heterocyclic ring system,

-   -   wherein each of the C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl or C₂₋₃₀-alkynyl         group may be substituted with 1 to 10 substituents independently         selected from the group consisting of halogen, —CN, —NO₂, —OH,         —NH₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂,         —NH—C(O)—(C₁₋₂₀-alkyl), —S(O)₂OH, —CHO, —C(O)—C₁₋₂₀-alkyl,         —C(O)OH, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁20 alkyl,         —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, —O—C(O)—C₁₋₂₀-alkyl,         —SiH₃, SiH₂(C₁₋₂₀-alkyl), SiH(C₁₋₂₀-alkyl)₂, Si(C₁₋₂₀-alkyl)₃,         C₄₋₈-cycloalkyl, phenyl and a 5 to 8 membered heterocyclic ring         system, and     -   phenyl or a 5 to 8 membered heterocyclic ring system may be         substituted with 1 to 5 C₁₋₁₆-alkyl groups, and         o is 1, 2 or 3         and         n is an integer from 2 to 10'000,         which process comprises the step of reacting a compound of         formula

wherein R¹ and R² are independently from each other C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl, C₂₋₃₀-alkynyl, phenyl or a 5 to 8 membered heterocyclic ring system,

-   -   wherein each of the C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl or C₂₋₃₀-alkynyl         group may be substituted with 1 to 10 substituents independently         selected from the group consisting of halogen, —CN, —NO₂, —OH,         —NH₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂,         —NH—C(O)—(C₁₋₂₀-alkyl), —S(O)₂OH, —CHO, —C(O)—C₁₋₂₀-alkyl,         —C(O)OH, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl,         —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, —O—C(O)—C₁₋₂₀-alkyl,         —SiH₃, SiH₂(C₁₋₂₀-alkyl), SiH(C₁₋₂₀-alkyl)₂, Si(C₁₋₂₀-alkyl)₃,         C₄₋₈-cycloalkyl, phenyl and a 5 to 8 membered heterocyclic ring         system, and     -   phenyl or a 5 to 8 membered heterocyclic ring system may be         substituted with 1 to 5 C₁₋₁₆-alkyl groups, and         X is triflate or halogen, preferably Br—,         with a compound of formula

wherein R³ and R⁴ are independently from each other H or C₁₋₁₀-alkyl, or R³ and R⁴ together with the —O—B—O— unit linking them form a cycle, preferably a five-membered cycle, which may be substituted with one or two C₁₋₆-alkyl, preferably methyl, M is an alkali metal, an alkaline earth metal or Al, m is 1, 2 or 3, o is 1, 2 or 3.

The compound of formula (2) is preferably reacted with the compound of formula (3) or (5) in the presence of transition metal catalyst I, preferably a palladium catalyst, and a base.

Examples of palladium catalysts are tetrakis(triphenyl)phosphinepalladium(0), palladium(II) chloride and palladium(II) acetate. Preferably, the palladium catalyst is palladium(II) acetate.

The base can be an amine, a metal or alkaline earth metal carbonate, a metal or alkaline earth metal acetate or an alkali or alkaline earth metal hydroxide. Examples of alkali or alkaline earth metal hydroxides are sodium, potassium and lithium hydroxide. Preferably, the base is an alkali or alkaline earth metal hydroxide. More preferably, the base is lithium hydroxide.

Preferably, a phosphine is also present in addition to the metal catalyst and the base. Examples of phosphines are triphenylphosphine, and, preferably, N-phenylpyrrole-P(tert-butyl)₂.

The reaction can be performed in the presence of an organic solvent such as tetrahydrofurane.

The reaction can be performed at elevated temperature, preferably in the range of 50 to 200° C., more preferably in the range of 50 to 120° C., most preferably in the range of 60 to 90° C.

Preferably, compound (2) is reacted with compound (3).

A preferred compound of formula (3) is the compound of formula

wherein o is 1, 2 or 3.

The compound of formula (2) may be prepared as described by Chen, Z.; Zheng, Y.; Yan, H.; Facchetti, A. J. Am. Chem. Soc. 2009, 31, 8-9 or by Sakai, N.; Sisson, A. L.; Buergi, T.; Matile, S. J. Am. Chem. Soc. 2007, 29, 15758-15759.

The compound of formula (3) may be prepared by reacting a compound of formula

wherein o is 1, 2 or 3 with (R³O)—B—(OR⁴) (6), wherein R³ and R⁴ are independently from each other H or C₁₋₁₀-alkyl, or R³ and R⁴ together with the —O—B—O— unit linking them form a cycle, preferably a five-membered cycle, which may be substituted with one or two C₁₋₆-alkyl, preferably methyl.

The compound of formula (3) is preferably reacted with the compound of formula (6) in the presence of transition metal catalyst II, preferably a zirconium catalyst, more preferably ZrCp₂HCl, also called Schwartz's reagent.

A preferred compound of formula (6) is

The reaction can be performed at elevated temperature, preferably in the range of 40 to 200° C., more preferably in the range of 40 to 100° C., most preferably in the range of 50 to 80° C.

The compound of formula (4) can be prepared by methods known in the art.

For example the preparation of the compound of formula

is described in Huang, E. Chem. Commun. 2011, 47, 11990-11992.

For example, the preparation of the compound of formula

is described by Neenan, Thomas X.; Whitesides, George M. J. Org. Chem., 1988, 53, 2489-2496.

Also part of the invention is an electronic device comprising the polymer comprising a unit of formula (1) as semiconducting material.

The electronic device can be any electronic device, for example an organic photovoltaic (OPV) cell, an organic field-effect transistor (OFET) or an organic light emitting diode (OLED). Preferably, the electronic device is an organic field-effect transistor.

Usually, an organic field effect transistor comprises a dielectric layer, a semiconducting layer and a substrate. In addition, an organic field effect transistor usually comprises a gate electrode and source/drain electrodes.

An organic field effect transistor can have various designs, for example bottom-gate design or top-gate design.

The semiconducting layer comprises the polymer of the present invention. The semiconducting layer can have a thickness of 5 to 500 nm, preferably of 10 to 100 nm, more preferably of 20 to 50 nm.

The dielectric layer comprises a dielectric material. The dielectric material can be silicon dioxide, or, an organic polymer such as polystyrene (PS), poly(methylmethacrylate) (PMMA), poly(4-vinylphenol) (PVP), poly(vinyl alcohol) (PVA), benzocyclobutene (BCB), or polyimide (PI). The dielectric layer can have a thickness of 10 to 2000 nm, preferably of 50 to 1000 nm, more preferably of 100 to 800 nm.

The source/drain electrodes can be made from any suitable source/drain material, for example silver (Ag), gold (Au) or tantalum (Ta). The source/drain electrodes can have a thickness of 1 to 100 nm, preferably from 5 to 50 nm.

The gate electrode can be made from any suitable gate material such as highly doped silicon, aluminium (Al), tungsten (W), indium tin oxide, gold (Au) and/or tantalum (Ta). The gate electrode can have a thickness of 1 to 200 nm, preferably from 5 to 100 nm.

The substrate can be any suitable substrate such as glass, or a plastic substrate such as polyethersulfone, polycarbonate, polysulfone, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Depending on the design of the organic field effect transistor, a combination of the gate electrode and the dielectric layer can also function as substrate.

The organic field effect transistor can be prepared by methods known in the art.

For example, a top-gate organic field effect transistor can be prepared as follows:

The source and drain electrodes can be formed by lithographically patterning a suitable source/drain material, for example Ag on a suitable substrate, example PET. The source/drain electrodes can then be covered with the semiconducting layer by solution processing, for example spin-coating, a solution of the semiconducting material of the present invention in a suitable solvent, for example in tetralin or toluene. The semiconducting layer can be covered with a dielectric layer by spin-coating a dielectric material, for example polystyrene, on the semiconducting layer. The gate electrode can be deposited on the dielectric layer for example by vapour deposition of a suitable source/drain material, for example gold (Au).

Also part of the invention is the use of the polymer comprising a unit of formula (1) as semiconducting material.

The polymers of the present invention show a high stability, in particular towards oxidation, under ambient conditions. The polymers of the present invention are compatible with liquid processing techniques and thus allow the production of low cost, light weight and flexible electronic devices. Organic devices, in particular organic field effect transistors, comprising the polymers of the present invention as semiconducting material show high charge carrier mobilities and on/off ratios.

EXAMPLES Example 1 Preparation of Polymer 1a

Preparation of Compound 3a

A mixture of 5,5′-diethynyl-2,2′-bithiophene (4a) (2.2 g, 10 mmol), pinacolborane (6a) (2.7 g, 21 mmol) and ZrCp₂HCl (Schwartz's reagent) (260 mg, 1 mmol) is sealed in a tube and stirred at 65° C. for 48 hours. Afterwards, the mixture is passed through silica gel pad and further purified on reverse phase column using hexane and ethyl acetate as eluent (hexane:ethyl acetate=10:1) to yield compound 3a as a white solid (2.1 g, 49%). ¹H NMR (400 MHz, CDCl₃) δ 7.39 (d, 2H, J=18 Hz), 7.07 (d, 2H, J=3.6 Hz), 7.97 (d, 2H, J=3.6 Hz), 5.97 (d, 2H, J=18 Hz), 1.50 (s, 24H).

Preparation of Polymer 1a

Compound 2a (300 mg, 0.31 mmol), compound 3a (180 mg, 0.38 mmol), N-phenylpyrrole-P(tert-butyl)₂ (18 mg, 0.06 mmol), Pd(OAc)₂ (3 mg, 0.02 mmol) and LiOH (96 mg, 2.29 mmol) are added to a Schlenk tube. The reaction vessel is evacuated and refilled with N₂ 3 times. Anhydrous THF (13 mL) is then added and heated under N₂ at 70° C. After 20 minutes, 1 drop of 2-bromothiophene is added and allowed to stir for 1 h. 1 drop of 2-thiophene boronic acid is added and the reaction mixture is allowed to stir at 70° C. for another 1 hour. The reaction mixture is precipitated in a large beaker of stirring MeOH (900 mL) for 1 hour before being filtered and the residue is subjected to Soxhlet extraction with acetone (250 mL) overnight until the extract is colorless. The residue is dried under vacuum, dissolved in minimum amount of hot chlorobenzene and precipitated in a beaker of stirring MeOH (900 mL) for 1 hour before being filtered and the residue is dried under vacuum overnight to yield polymer 1a (310 mg, 97%). ¹H NMR (400 MHz, DCE, r.t.) δ 9.06 (brs, 2H), 8.74 (d, 2H, 15.6 Hz), 7.64 (d, 2H, 15.6 Hz), 7.27-7.03 (m, 4H), 4.25 (br, 4H), 2.40 (br, 2H), 1.49-1.17 (m, 64H), 1.01-0.90 (brs, 12H). Mn: 3.44×10⁴, PDI: 2.06.

Example 2 Preparation of Polymer 1b

Preparation of Compound 3b

A mixture of 2,5-diethynylthiophene (4b) (1.4 g, 10 mmol), pinacolborane (6a) (2.8 g, 21 mmol) and ZrCp₂HCl (Schwartz's reagent) (260 mg, 1 mmol) is sealed in a tube and stirred at 65° C. for 70 hours. Afterwards, the mixture is passed through silica gel pad and further purified on reverse phase column using hexane and ethyl acetate as eluent (hexane:ethyl acetate=15:1) to yield compound 3b as a white solid (1.55 g, 40%). ¹H NMR (400 MHz, CDCl₃) δ 7.38 (d, 2H, J=18 Hz), 6.95 (s, 2H), 5.91 (d, 2H, J=18 Hz), 1.50 (s, 24H).

Preparation of Polymer 1b

Compound 2a (450 mg, 0.46 mmol), compound 3b (177 mg, 0.46 mmol), N-phenylpyrrole-P(tert-butyl)₂ (21 mg, 0.07 mmol), Pd(OAc)₂ (4 mg, 0.02 mmol) and LiOH (115 mg, 2.74 mmol) are added to a Schlenk tube. The reaction vessel is evacuated and refilled with N₂ 3 times. Anhydrous THF (11 mL) is then added and heated under N₂ at 70° C. After 22 hours, 1 drop of 2-bromothiophene is added and allowed to stir for 1 hour. 1 drop of 2-thiophene boronic acid is added and the reaction mixture is allowed to stir at 70° C. for another 4 hours. The reaction mixture is precipitate in a large beaker of stirring MeOH (900 mL) for 1 hour before being filtered and the residue is subjected to Soxhlet extraction with acetone (250 mL) overnight until the extract is colorless. The residue is dried under vacuum, dissolved in minimum amount of hot chlorobenzene and precipitated in a beaker of stirring MeOH (900 mL) for 1 hour before being filtered and the residue is dried under vacuum overnight to yield polymer 1b. (330 mg, 73%). ¹H NMR (400 MHz, DCE, r.t) δ 9.06 (brs, 2H), 8.70 (d, 2H, 15.6 Hz), 7.58 (d, 2H, 15.6 Hz), 7.52-7.40 (m, 2H), 4.29 (br, 4H), 2.14 (br, 2H), 1.50-1.34 (m, 64H), 1.01-0.90 (brs, 12H). Mn: 2.85×10⁴, PDI: 2.25.

Example 3 Preparation of a Top-Gate Bottom-Contact Field-Effect Transistors Comprising the Polymer 1a, Respectively, 1b as Semiconducting Material

The polymer 1a is dissolved in toluene (5 mg/ml) and spin coated on a PET substrate with litographically patterned silver (Ag) contact (W/L=1000, L=10 μm) at 1500 rpm for 1 minute followed by drying on a 110° C. hotplate for 2 minute.

The polymer 1b is dissolved in tetralin (5 mg/ml) and spin coated (heated solution and substrate at 110° C.) on a PET substrate with litographically patterned silver (Ag) contact (W/L=1000, L=10 μm) at 1000 rpm for 2 minute followed by drying on a 110° C. hotplate for 2 minute.

In both cases, polystyrene is used as gate dielectric (4 wt % in isopropyl actetate) and is deposited by spin coating at 3600 rpm for 30 sec followed by drying on a 90° C. hotplate for 30 sec. All the depositions are done in ambient atmosphere. Finally gold (Au) is deposited by thermal evaporation for use as gate electrode. The thickness of the semiconducting layer is 30 nm, and the thickness of the dielectric layer is 420 nm.

Average charge carrier mobility of the transistor comprising the polymer 1a is 0.03 cm²Ns with on/off ratio of 10⁵, while the charge carrier mobility of the transistor comprising the polymer of formula 1b is 0.04 cm²Ns with on/off ˜10⁴. 

The invention claimed is:
 1. A polymer comprising a unit of formula

wherein R¹ and R² are independently from each other C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl, C₂₋₃₀-alkynyl, phenyl or a 5 to 8 membered heterocyclic ring system, wherein each of the C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl or C₂₋₃₀-alkynyl group may be substituted with 1 to 10 substituents independently selected from the group consisting of halogen, —CN, —NO₂, —OH, —NH₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂, —NH—C(O)—(C₁₋₂₀-alkyl), —S(O)₂OH, —CHO, —C(O)—C₁₋₂₀-alkyl, —C(O)OH, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, —O—C(O)—C₁₋₂₀-alkyl, —SiH₃, SiH₂(C₁₋₂₀-alkyl), SiH(C₁₋₂₀-alkyl)₂, Si(C₁₋₂₀-alkyl)₃, C₄₋₈-cycloalkyl, phenyl and a 5 to 8 membered heterocyclic ring system, and phenyl or a 5 to 8 membered heterocyclic ring system may be substituted with 1 to 5 C₁₋₁₆-alkyl groups, o is 2 or 3 and n is an integer from 2 to 10,000.
 2. The polymer of claim 1, wherein R¹ and R² are independently from each other C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl, C₆₋₃₀-alkynyl, or phenyl, wherein each of the C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl groups may be substituted with 1 to 10 substituents independently selected from the group consisting of halogen, —CN, —NO₂, —OH, —NH₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂, —NH—C(O)—(C₁₋₂₀-alkyl), —S(O)₂OH, —CHO, —C(O)—C₁₋₂₀-alkyl, —C(O)OH, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, and N—O—C(O)—C₁₋₂₀-alkyl, and phenyl may be substituted with 1 or 2 C₁₋₁₆-alkyl groups.
 3. The polymer of claim 1, wherein R¹ and R² are independently from each other C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl, wherein each of the C₆₋₃₀-alkyl, C₆₋₃₀-alkenyl or C₆₋₃₀-alkynyl group may be substituted with 1 to 10 substituents independently selected from the group consisting of halogen, —CN, —NO₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂, —NH—C(O)—(C₁₋₂₀-alkyl), —C(O)—C₁₋₂₀-alkyl, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, and N—O—C(O)—C₁₋₂₀-alkyl.
 4. The polymer of claim 1, wherein R¹ and R² are independently from each other C₆₋₃₀-alkyl, wherein each of the C₆₋₃₀-alkyl may be substituted with 1 to 10 substituents independently selected from the group consisting of halogen, —CN, —NO₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂, —NH—C(O)—(C₁₋₂₀-alkyl), —C(O)—C₁₋₂₀-alkyl, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, and N—O—C(O)—C₁₋₂₀-alkyl.
 5. The polymer of claim 1, wherein R¹ and R² are independently from each other C₁₀₋₃₀-alkyl.
 6. The polymer of claim 5, wherein R¹ and/or R² are independently from each other 2-octyldodecyl.
 7. The polymer of claim 1, wherein o is
 2. 8. The polymer of claim 1, wherein n is an integer from 5 to 1,000.
 9. The polymer of claim 1, wherein n is an integer from 5 to
 500. 10. The polymer of claim 1, wherein n is an integer from 10 to
 100. 11. The polymer of claim 1 comprising a unit of formula

wherein n is an integer from 20 to
 100. 12. An electronic device comprising the polymer of claim 1 as semiconducting material.
 13. The electronic device of claim 12, wherein the electronic device is an organic field effect transistor.
 14. The electronic device of claim 12, wherein the electronic device is an organic photovoltaic device.
 15. A semiconducting material comprising the polymer of claim
 1. 16. A process for the preparation of the polymer of claim 1, comprising reacting a compound of formula

wherein R¹ and R² are independently from each other C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl, C₂₋₃₀-alkynyl, phenyl or a 5 to 8 membered heterocyclic ring system, wherein each of the C₁₋₃₀-alkyl, C₂₋₃₀-alkenyl or C₂₋₃₀-alkynyl group may be substituted with 1 to 10 substituents independently selected from the group consisting of halogen, —CN, —NO₂, —OH, —NH₂, —NH(C₁₋₂₀-alkyl), —N(C₁₋₂₀-alkyl)₂, —NH—C(O)—(C₁₋₂₀-alkyl), —S(O)₂OH, —CHO, —C(O)—C₁₋₂₀-alkyl, —C(O)OH, —C(O)—OC₁₋₂₀-alkyl, —C(O)NH₂, —CO(O)NH—C₁₋₂₀-alkyl, —C(O)N(C₁₋₂₀-alkyl)₂, —O—C₁₋₂₀-alkyl, —O—C(O)—C₁₋₂₀-alkyl, —SiH₃, SiH₂(C₁₋₂₀-alkyl), SiH(C₁₋₂₀-alkyl), Si(C₁₋₂₀-alkyl)₃, C₄₋₈-cycloalkyl, phenyl and a 5 to 8 membered heterocyclic ring system, and phenyl and the 5 to 8 membered heterocyclic ring system may be substituted with 1 to 5 C₁₋₁₆-alkyl groups, and X is triflate or halogen, with a compound of formula

wherein R³ and R⁴ are independently from each other H or C₁₋₁₀-alkyl, or R³ and R⁴ together with the —O—B—O— unit linking them form a cycle which may be substituted with one or two C1-6-alkyl, M is an alkali metal, an alkaline earth metal or Al, m is 1, 2 or 3, o is 2 or
 3. 17. The process of claim 16, wherein X is Br.
 18. The process of claim 16, wherein R³ and R⁴ together with the —O—B—O— unit linking them form a five-membered cycle.
 19. The process of claim 16, wherein R³ and R⁴ together with the —O—B—O— unit linking them form a five-membered cycle, which is substituted with one or two C1-6-alkyl.
 20. The process of claim 19, wherein the five-membered cycle is substituted with one or two methyl. 